Strategic Metals Research Articles

Chemical mutation of Bacillus mucilaginosus genes to enhance the bioleaching of vanadium-bearing shale

The recovery and utilization of vanadium from vanadium-bearing shale are significant because vanadium is an important strategic metal. This study explored a cleaner metal extraction method to recover vanadium from vanadium-bearing shale using a novel strain of mutated Bacillus mucilaginosus (B.M) for an enhanced bioleaching process. The highly efficient bioleaching bacterium B.M-0.2 was obtained by chemical mutation using hydroxylamine hydrochloride. The optimal conditions for vanadium extraction by the mutagenized bacteria were 0.5 g/L ammonium nitrate, 5 g/L sucrose, pH 7.5, ore particle size of less than 0.074 mm accounting for 92.34% of the total, and pulp density of 10 g/L. Under these conditions, the vanadium leaching efficiency of B.M-0.2 was 8.16% higher than that of the original bacteria after a bioleaching period of 30 days. The Organic acid test results also showed that the mutant B.M-0.2 had notably high acid production. The genome of the mutant B.M-0.2 was sequenced via polymerase chain reaction, which revealed clear changes. Through KEGG pathway analysis, pathways related to the proteins that were differentially expressed between the two were also revealed. The results showed that the B.M mutated chemically using hydroxylamine hydrochloride has great potential to improve the recovery of vanadium from vanadium-bearing shale.

Technospheric mining of critical and strategic metals from nickel slag – Leaching with citric acid and hydrogen peroxide

Critical and strategic metals (CSMs), such as cobalt (Co) and nickel (Ni), are fundamental components of the high technology industry. Securing the supply of CSMs is fast becoming a priority for nations. Thus, secondary sources such as mine wastes, slags, tailings, and residues are being exploited to extract CSMs since they contain notable amounts of those metals. Recovering valuable metals from secondary sources can be categorised as technospheric mining. In this study, the extraction of cobalt and nickel from nickel slag was examined using a combination of an organic acid, citric acid, and hydrogen peroxide as the oxidant. Optimum conditions consisted of 1 M citric acid, 0.5% (v/v) hydrogen peroxide, at a temperature of 60 °C, a pulp density of 2.5%, a particle size of −100 + 75 μm, and an agitation speed of 400 rpm, for a period of 6 h. At the optimum conditions, 84.0% Ni and 91.7% Co were extracted from flash furnace (FF) slag, and 65.0% Ni and 99.1% Co from converter (CV) slag. It is expected that a combination of citric acid and hydrogen peroxide created peroxycitric acid in the solution, which is a strong oxidant and a key factor in the dissolution of the metals. The leach residue from FF slag showed a porous surface resulting from preferential dissolution within the slag structure. The residue from the converter (CV) slag mainly consisted of magnetite as a result of the dissolution of fayalite (Fe2SiO4). The kinetic studies demonstrated that the dissolution of Ni and Co from FF slag is controlled by diffusion. On the other hand, a rate controlling factor for Ni from CV slag is mixed control and for Co is a chemical reaction. Based on the temperature varied experiments, the calculated activation energy for Ni and Co from FF slag were 34.4 kJ/mol and 27.6 kJ/mol, respectively. The activation energies for the leaching of Ni and Co from the CV slag were 16.1 kJ/mol and 23.7 kJ/mol, respectively.

Multi-Component Resource Recycling from Waste Light-Emitting Diode Under Hydrothermal Condition: Plastic Package Degradation, Speciation of Nano-TiO2, and Environmental Impact Assessment

Light emitting diodes (LEDs) have accounted for most of the lighting market as the technology matures and costs continue to reduce. As a new type of e-waste, LED is a double-edged sword, as it contains not only precious and rare metals but also organic packaging materials. In previous studies, LED recycling focused on recovering precious and strategic metals while ignoring harmful substances such as organic packaging materials. Unlike crushing and other traditional methods, hydrothermal treatment can provide an environment-friendly process for decomposing packaging materials. This work developed a closed reaction vessel, where the degradation rate of plastic polyphthalamide (PPA) was close to 100%, with nano-TiO2 encapsulated in plastic PPA being efficiently recovered, while metals contained in LED were also recycled efficiently. Besides, the role of water in plastic PPA degradation that has been overlooked in current studies was explored and speculated in detail in this work. Environmental impact assessment revealed that the proposed recycling route for waste LED could significantly reduce the overall environmental impact compared to the currently published processes. Especially the developed method could reduce more than half the impact of global warming. Furthermore, this research provides a theoretical basis and a promising method for recycling other plastic-packaged e-waste devices, such as integrated circuits.

Near-Bottom Magnetic Anomaly Features and Detachment Fault Morphology in Tianxiu Vent Field, Carlsberg Ridge, Northwest Indian Ocean

As a product of hydrothermal mineralization at spreading centers, seafloor massive sulfides (SMS) have become a research hotspot in the field of prospecting and exploring deep-sea mineral resources owing to their enrichment of various strategic metals. Since hydrothermal circulation changes the magnetic properties of host rocks and can generate magnetic anomalies, near-bottom magnetic surveying is an effective method to determine magnetic anomaly features of the seafloor. This technology has been applied to the detection of SMS deposits, in addition to its use in understanding hydrothermal fluid flow conduits and associated hydrothermal alterations. The Tianxiu Vent Field (TVF) is a detachment-fault-controlled, ultramafic-associated hydrothermal system located on the Carlsberg Ridge, Northwest Indian Ocean. During China’s DY57th cruise in 2019, near-bottom magnetic data were collected by an autonomous underwater vehicle. In this paper, we use bathymetric and magnetic data, as well as rock sampling information, to analyze and discuss the magnetic anomaly features of the TVF region. Then, we apply 2.5D magnetic anomaly profile forward modeling to determine the shallow magnetic structure and the pattern of detachment faults in the subsurface. Our results show that TVF is characterized by a significant positive magnetic anomaly, where stronger magnetization exists in the area with active hydrothermal vent clusters. The detachment fault has a dip of less than 30° at shallow depths, which steepens to a dip of ~70° at depths of around 300 m.

Preparation of High-Purity Magnesium from Electrolytically Produced Crude Magnesium via Vacuum Distillation

Metallic Mg is an important strategic metal and its properties are greatly affected by impurities. Silicothermic reduction and electrolysis are the most used approaches to prepare metallic Mg. The products of these processes need to be further refined to obtain high-purity Mg metal. However, previous research has mainly focused on refining the crude Mg (CM) produced via silicothermic reduction, whereas no in-depth investigations have been conducted on refining the CM produced via electrolysis. Here, vacuum distillation was used to refine electrolytically produced CM. The content and morphological characteristics of the impurity elements in CM were studied via glow discharge mass spectrometry, mineral dissociation analysis, and electron probe microanalysis. The effect of different distillation temperatures and times on the quality of the refined Mg was investigated. The results show that the main impurity elements are Al, Fe, Si, Ti, Cr, S, Cl, and Ni. The content of impurities, such as Si, Al, Fe, Ni, Ti, and Cr, in the refined Mg is significantly reduced at a temperature of 1023 K and a time of 120 min, and the purity of the refined Mg reaches 99.99%, which meets the Mg9999 national standard for primary Mg ingots in China (GB/3499-2011).

Investigating price fluctuations in copper futures: Based on EEMD and Markov-switching VAR model

Predictable global copper prices are crucial to the transition to a green economy. This paper examines the nonlinear characteristics between the international copper futures prices and their drivers, using combined Empirical Mode Decomposition (EEMD) and the Markov-switching VAR (MSVAR) models. We decompose the monthly international copper futures prices from January 2015 to October 2021 into its low-frequency and high-frequency components by using the EEMD method. In the next step, we employ the MSVAR to examine the nonlinear fluctuation of the international copper futures prices under different regimes. The results indicate that fluctuations of the international copper futures prices exhibit a dynamic regime switching patterns that is characterized as “expansion”, “plateau” and “contraction”. The long-term stability of the international copper futures prices is determined by factors associated with demand, especially demand for strategic metals. Both the London Metal Exchange (LME) copper stocks and the LME copper stock futures have a significant impact on the international copper futures prices in each regime. In several regimes, the global refined copper consumption has no significant effect on the international copper futures prices. The increase in copper turnover is the primary driver of the international copper futures prices during the contraction regime. Regarding the supply factor, an increase in global refined copper capacity would result in a rise in the international copper futures prices during the expansion regime. While a slump would occur during a plateau or contraction regime. The financial factor, reflected by non-commercial traders affects the international copper futures prices volatility differently under different regimes. The increase in speculation reduces the market volatility during regimes of expansion and contraction. In contrast, in plateau regime, speculation increases market volatility and activates the market. The broad dollar index has little impact on the international copper futures prices during each regime. The above conclusions indicate that we should focus on the fluctuations in the international copper futures prices that are caused by the demand for strategic metals and financial factors.

Introducing heterotrophic iron ore bacteria as new candidates in promoting the recovery of e-waste strategic metals.

Electrical instruments are an integral part of human life resulting in a vast electronic waste generation (74.7 Mt by 2030), threatening human life and the environment due to its hazardous nature. Therefore, proper e-waste management is a necessity. Currently, bio-metallurgy is a sustainable process and an emerging research field. Simultaneous leaching of metals using two groups of indigenous heterotrophs and autotrophs was an exciting work done in this study. Bioleaching experiments using pre-adapted cultures were investigated at three e-waste densities: 5, 10, and 15g/L. Statistical analysis was done using two-way ANOVA. Copper (93%), zinc (21.5%), and nickel (10.5%) had the highest recovery efficiencies. There was a significant difference between copper, nickel, tin, and zinc concentrations and the bacterial group (P < 0.05); Iron-oxidizing bacteria showed the most weight decrease and recovered 46-47% of total metals, mainly copper and nickel, while sulfur oxidizers were more capable of zinc leaching. The heterotrophs solubilized tin preferably and substantially decreased e-waste weight. Using heterotrophs alongside autotrophs is proposed to promote metal recovery.

The role of the electrolyte in non-conjugated radical polymers for metal-free aqueous energy storage electrodes.

Metal-free aqueous batteries can potentially address the projected shortages of strategic metals and safety issues found in lithium-ion batteries. More specifically, redox-active non-conjugated radical polymers are promising candidates for metal-free aqueous batteries because of the polymers' high discharge voltage and fast redox kinetics. However, little is known regarding the energy storage mechanism of these polymers in an aqueous environment. The reaction itself is complex and difficult to resolve because of the simultaneous transfer of electrons, ions and water molecules. Here we demonstrate the nature of the redox reaction for poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl acrylamide) by examining aqueous electrolytes of varying chao-/kosmotropic character using electrochemical quartz crystal microbalance with dissipation monitoring at a range of timescales. Surprisingly, the capacity can vary by as much as 1,000% depending on the electrolyte, in which certain ions enable better kinetics, higher capacity and higher cycling stability.

Selective extraction of gold from strong acid E-waste leachate through H+-triggered cascade reaction of thiolated β-cyclodextrin

Recycling precious metals from the increasing amount of e-waste is significant for the sustainability of strategic metal resources. However, few technologies have been reported for efficient and highly selective recovery of precious metals from the strong acidic e-waste leachate. Herein, we demonstrated a simply synthesized thiolated β-cyclodextrin (T-CD) that can recover gold from multi-metal coexistence solutions at pH 2 with an exceptional adsorption capacity of 1890.98 mg/g, and a superior selectivity coefficient about 5×104. The recognition of Au3+ by sulfhydryl groups on T-CD and the hydrolysis of T-CD triggered by H+ were proved to be the critically important contributors to the highly selective recovery of gold from strong acid wastewater. In addition, T-CD can directly and effectively extract gold from actual waste PCB leachate, allowing the acidic solution to be recycled five times. This work provides a new guidance for the direct recovery of rare metals from strongly acidic wastewater.

High-value utilisation of PGM-containing residual oil: Recovery of inorganic acids, potassium, and PGMs using a zero-waste approach

Residual oil containing platinum group metals (PGMs), which is under-researched, can easily pose resource waste and environmental risks. PGMs feature as scarce strategic metals, and inorganic acids and potassium salts are also considered valuable. An integrated process for the harmless treatment and recovery of useful resources from residual oil is proposed herein. This work developed a zero-waste process based on the study of the main components and characteristics of the PGM-containing residual oil. The process consists of three modules: pre-treatment for phase separation, liquid-phase resource utilisation, and solid-phase resource utilisation. Separating the residual oil into liquid and solid phases allows for the maximum recovery of valuable components. However, concerns about the accurate determination of valued components emerged. Findings revealed that Fe and Ni are highly susceptible to spectral interference in the PGMs test when using the inductively coupled plasma method. After studying 26 PGM emission lines, Ir 212.681 nm, Pd 342.124 nm, Pt 299.797 nm, and Rh 343.489 nm were reliably identified. Finally, formic acid (81.5 g/t), acetic acid (117.2 kg/t), propionic acid (291.9 kg/t), butyric acid (3.6 kg/t), potassium salt (553.3 kg/t), Ir (27.8 g/t), Pd (10960.0 g/t), Pt (193.1 g/t), and Rh (109.8 g/t) were successfully obtained from the PGM-containing residual oil. This study provides a helpful reference for the determination of PGM concentrations and high-value utilisation of PGM-containing residual oil.

Review of preferentially selective lithium extraction from spent lithium batteries: Principle and performance

Lithium, as the lightest and lowest potential metal, is an ideal “battery metal” and the core strategic metal of the new energy industry revolution. Recovering lithium from spent lithium batteries (LIBs) has become one of the significant approaches to obtaining lithium resources. At present, the lithium extraction being generally placed at the last step of the spent LIBs recovery process has puzzles such as high acid consumption, low Li recovery purity and low recovery efficiency. Selective lithium extraction at the first step of the recovery process can effectively solve those puzzles. Since lithium leaching is a non-spontaneous reaction requiring additional energy to achieve, it is found that these methods can be divided into five ways according to the different types of energy driving the reaction occurring: (i) electric energy driving lithium extraction; (ii) chemical energy driving lithium extraction; (iii) mechanical energy driving lithium extraction; (iv) thermal energy driving lithium extraction; (v) other energy driving lithium extraction. Through the analysis of the principle, reaction process and results of recovering lithium methods can provide a few directions for scholars' subsequent research. It is necessary to speed up the exploration of the principle of these methods. It is expected that this study could provide a reference for the research on the selective lithium extraction.

Challenges and opportunities for sustainable valorization of rare earth metals from anthropogenic waste.

Progressively and projected integration of rare earth metals (REMs) in modern technologies, especially in the clean energy, consumer electronics, aerospace, automotive, and defense sectors, place REMs as critical raw materials in the supply chain and strategic metal from the fourth industrial revolution perspective. Current REM production from the primary mineral resources in the supply chain versus industrial demand is at a bottleneck. Alternatively, REM-bearing anthropogenic wastes are pertinent and potent to addressing the critical supply chain bottleneck. Although secondary REM resources are prudent to address the critical supply chain bottleneck, the absence of effective and efficient technologies to recover these REMs from anthropogenic waste imposes challenges and provides opportunities. Hence, this review analyses and discusses the significance of anthropogenic wastes for REM recovery, the status of recycling technologies for sustainable valorization of REMs, challenges, and opportunities. The current review covers the potential quantitative REM wealth locked in various anthropogenic waste like (i) spent rare earth permanent magnets, (ii) spent batteries, (iii) spent tri-band REM phosphors, (iv) bauxite industry residue red mud, (v) blast furnace slag and (v) coal mines, and coal byproducts and status of valorization technologies for circularizing the REMs. In industrial waste like red mud, steelmaking slag, blast furnace slag, and coal fly ash typically 109,000, 2000, 39,000, and 354,000 tons of REM get scrapped, respectively, in a conservative estimation. In the years 2020 and 2021, respectively, 240,000 and 280,000 tons of REM were produced by mine production in contrast to 504,000 tons of REM that were scrapped with REM-bearing industrial waste. This review revealed that total REM currently getting scrapped with anthropogenic waste versus projected REM demand for the years 2022, 2023, 2024, and 2025 could be standing at 2.66, 2.51, 2.37, and 2.23, respectively. Our investigation revealed that efficient recovery of REMs from anthropogenic waste is significant and promising but associated with challenges like lack of industrial-scale valorization process, lack of a clear strategy, road map, policy, effort, funding, and diversified research.

Rhenium extraction from pressure oxidative leaching solution of molybdenite concentrate using hydrophobic deep eutectic solvents

This research is one of the early studies to evaluate the capability of hydrophobic deep eutectic solvents (DESs) as an eco-friendly solvent for precious and strategic metal extraction, rhenium (Re). In this study, the selective transfer of Re from aqueous solution and pressure oxidative leaching solution of molybdenite concentrate was investigated by mixing fatty acid (Decanoic acid) and quaternary ammonium salt (Aliquat 336). To evaluate the extraction potential of hydrophobic-DES in the ratio of Decanoic acid (Deca):Aliquat 336 = 2:1, FTIR, 1H NMR, thermal gravimetric analysis was used. For finding an optimum condition for Re separation, various extraction conditions were initially investigated in synthetic aqueous solution. In this area, the maximum extraction percentage was obtained at a concentration of Re = 100 mg/L, ratio of organic to aqueous phase (O:A) = 1 to 25, contact time = 10min, pH = −0.5, and temperature = 25°C. In the stripping step, the recovery of >90% Re at selected O:A = 5:1 showed that significant reduction of water consumption. After that, the complex situation for selective Re extraction from molybdenite leaching solutions with different cations and anions was studied. For increasing the extraction and separation factor of Re in comparison to the other ionic specious (e.g., Cu, Fe, Mo and S), the neutralization process was also applied. To understand the extraction mechanism for Re, anion exchange constant (KOE) and ion pair constant (KIP) were determined. In this area, the ion pair formation was chosen as the main reaction mechanism; however, anion exchange reaction was not negligible role in Re extraction. Toxicity study on hydrophobic-DES was investigated by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. The obtained results according to IC50 and viability of cells culture represented the low toxicity of hydrophobic-DES.

Locked up Inside the Vessels: Rare Earth Elements Are Transferred and Stored in the Conductive Tissues of the Accumulating Fern Dryopteris erythrosora.

Rare earth elements (REEs) are strategic metals strongly involved in low-carbon energy conversion. However, these emerging contaminants are increasingly disseminated into ecosystems, raising concern regarding their toxicity. REE-accumulating plants are crucial subjects to better understand REE transfer to the trophic chain but are also promising phytoremediation tools. In this analysis, we deciphered REE accumulation sites in the REE-accumulating fern Dryopteris erythrosora by synchrotron X-ray μfluorescence (μXRF). This technique allows a high-resolution and in situ analysis of fresh samples or frozen-hydrated cross sections of different organs of the plant. In the sporophyte, REEs were translocated from the roots to the fronds by the xylem sap and were stored within the xylem conductive system. The comparison of REE distribution and accumulation levels in the healthy and necrotic parts of the frond shed light on the differential mobility between light and heavy REEs. Furthermore, the comparison emphasized that necrotized areas were not the main REE-accumulating sites. Finally, the absence of cell-to-cell mobility of REEs in the gametophyte suggested the absence of REE-compatible transporters in photosynthetic tissues. These results provide valuable knowledge on the physiology of REE-accumulating ferns to understand the REE cycle in biological systems and the expansion of phytotechnologies for REE-enriched or REE-contaminated soils.

Recycling Strategy toward Efficient and Green Lithium Leaching from Coal-Based Lithium Ores Enabled by Solubility Engineering and Reusable Solid Acid

Lithium is an important strategic metal, but the supply of lithium ore is growing slowly, which is in sharp contradiction with the rapidly growing demand. Therefore, it is urgent to find new lithium resources. Recently, it has been found that coal-based lithium ore is expected to become a new type of lithium resource to meet the rapidly growing demand for lithium. However, the traditional Li extraction process using inorganic acids (i.e., H2SO4) is facing serious environmental issues, and the excess acid needs to be neutralized before the subsequent purification process. Herein, for the first time, we proposed a novel recycling strategy for the efficient and scalable Li leaching from coal-based Li ores with a reusable solid acid (oxalic acid), in which oxalic acid can be easily recovered after the leaching process with facile solubility engineering. The influences of the leaching conditions and oxalic acid concentration on the Li leaching and recycling rates of oxalic acid were explored in detail. Under the optimal conditions, the Li leaching rate (89.12%) and recovery rate (88.12%) of oxalic acid reached nearly 90%. In addition, the results of X-ray diffraction and Fourier-transform infrared clearly proved the high purity of the recovered oxalic acid after Li leaching, and the recovered oxalic acid also possessed excellent leaching performance after five times of recycling experiments. Moreover, the leaching kinetic analysis showed that the Li extraction from coal-based Li ore with oxalic acid was a chemical-controlled process with an activation energy (Ea) of 74.42 kJ/mol. Therefore, with solubility engineering, the recycling of oxalic acid after Li leaching could be easily realized, which is possible for other solid acids and provides a promising strategy for the simultaneous realization of green Li extraction and leaching acid recovery.

Brown Algal Residue for the Recovery of Metal Ions—Application to La(III), Cd(II), and Ni(II) Sorption

AbstractRemoving hazardous metals and recovering valuable strategic metals from wastewater has become an important challenge for the industry. Herein, brown algal biomass residue (AR, after bio‐stimulant extraction, currently poorly valorized) is tested for the removal of Ni(II), Cd(II), and La(III) from aqueous solutions. This valorization of industrial waste makes profit of residual amounts of alginate‐based materials, which have a strong affinity for metal cations. Fourier transform infrared (FTIR) and X‐ray photoelectron spectroscopy (XPS) techniques are used for characterizing metal/biosorbent interactions. Uptake kinetics are relatively fast (equilibrium being reached in 180–240 min). The Sips equation fits the sorption isotherms; the maximum sorption capacities at pH ≈5 reach up to 0.84 mmol La g−1, 0.92 mmol Cd g−1, and 0.78 mmol Ni g−1. In binary solutions, AR shows marked preference for La(III) over divalent cations. This selectivity may be increased by complexing base metals with EDTA, opening the route for the selective recovery of rare earth elements. HCl solution reveals more efficient (&gt;90% for La(III), ≈82% for Cd(II) and Ni(II)) than CaCl2 solution at pH 2 for metal desorption. This waste residue from biostimulant extraction (in brown algal biomass) can be valorized for the recovery of hazardous and strategic metal ions.

Gallium and other valuable components recovery from phosphorus flue dust by a novel process combining vacuum chlorination and water leaching

Gallium (Ga) is an important strategic metal widely used in the semiconductor manufacturing industry. In this paper, a new vacuum chlorination and water leaching process for simultaneous P fixation and Ga, Pb, and Zn separation from phosphorus flue dust (PFD) using CaCl2 as reagent was proposed. The principle of metal volatilization in vacuum was clarified and the reaction mechanism of chlorination was studied. The impacts of the experimental parameters on the metals volatilization rate were assessed. Under the optimal conditions, Ga volatilization rate reached 97.44 %, the volatilization rates of Pb and Zn respectively reached 98.11 %, and 98.56 % and were highly enriched in the condensation zone, while most of P was converted into water-insoluble Ca2P2O7 and remained in the residue. In addition, the impacts of several factors in the water leaching process on the removal of Cl from the residue were studied. Finally, the leaching solution mainly containing Cl-, K+, and Ca2+ and the water leaching residue with P content of 19.21 % were obtained. This process provides a new clean and sustainable method for the recovery of valuable components in PFD, without the generation of hazardous substances, and therefore it has potential application value.

The State of Critical and Strategic Metals Recovery and the Role of Nuclear Techniques in the Separation Technologies Development: Review

The extraction of useful minerals or geological materials from the Earth’s crust, most typically from various sources, is crucial to a country’s development and progress. Mineral-rich countries use these resources to transform their economies and propel them toward long-term prosperity. There is an urgent need for the world to increase mineral exploration efforts, improve the recycling of important metal-containing resources, and extract them using upgraded hydrometallurgical procedures with high recovery efficiency. This review paper highlights the importance of strategic and critical metals in the economy and the role of nuclear techniques in the analysis, process optimization, and remediation of metals using solvent extraction, adsorption, and chromatographic resins. Radiotracer analysis, X-Ray Fluorescence spectrometry (XRF), Neutron Activation Analysis (NAA), and X-Ray Diffraction (XRD) are appropriate for improving laboratory-based hydrometallurgical processes, with future technical and economic benefits. The development and installation of novel instruments to provide the real-time control of mining and mineral processing plants for improved control have the potential to aid in the recovery of a broad range of metals.

Extraction of Sodium Tungstate from Tungsten Ore by Pyrometallurgical Smelting

Tungsten is one of the strategic metals produced from tungsten ores through sodium tungstate. The hydrometallurgical process is a common technology for extracting sodium tungstate from high-grade tungsten concentrates. The grade of tungsten ore is decreasing, and the mineral processing to produce a high-grade concentrate suitable for the hydrometallurgical process is becoming more difficult. It is desirable to develop a new technology to effectively recover tungsten from the complex low-grade tungsten ores. A fundamental study on the pyrometallurgical processing of wolframite was carried out through thermodynamic calculations and high-temperature experiments. The wolframite was reacted with Na2CO3 and SiO2 at 1050–1200 °C and then leached with water to obtain a sodium tungstate solution as a feed for the traditional process of APT (Ammonium paratungstate). The factors affecting the extraction rate of tungsten from wolframite were investigated in air and neutral atmosphere. The extraction rate of tungsten was found to increase with increasing Na2O content and decrease with increasing SiO2 addition and temperature. The extraction rate in argon was higher than that in air for wolframite.

Securing Indium Utilization for High-Tech and Renewable Energy Industries.

Indium has emerged as a strategic metal for high-tech and renewable industries, being catalogued as a critical material to foster a greener future. Nevertheless, its global sustainability is not well addressed. Here, using dynamic substance flow analysis, we study the indium industry evolution between 2010 and 2020 and estimate its future demand in the medium and long term toward 2050 to identify potential paths and mechanisms to decrease indium losses and to identify the key stages in its life cycle. As electronics and photovoltaic industries will play a crucial role in the indium demand, we assess their indium demand employing three cumulative photovoltaic capacity scenarios (8.5, 14, and 60 TW by 2050) with different dominant photovoltaic sub-technologies. Results show that liquid-crystal displays and photovoltaic panels will drive indium future demand, increasing its current demand by 2.2-4.2, 2.6-7.0, and 6.8-38.3 times for the 8.5, 14, and 60 TW scenarios, respectively, threatening with shortages that could occur as early as the next decade. Therefore, measures to reduce losses in primary production, innovations and improvements in electronics and solar panels, and indium recycling with an effective circular economy strategy could promote and secure the future sustainability of indium.